A
arktype•2w ago
Bobakanoosh

Passing schemas to functions that are piped

I have a bunch of incoming events that I need to parse and validate. They all have a common structure. I'm wanting to build a more generic system where you can pass what events to "subscribe" to. This was working great until I had an event that had a .pipe(). Any ideas how I can get around this? 
const BaseEvent = type({
    type: "string",
    timestamp: "number",
});

const SomeEvent = BaseEvent.and({
    type: "'some_event'",
    data: {
        foo: "string",
    },
});

const SomePipedEvent = BaseEvent.and({
    type: "'some_piped_event'",
    data: {
        bar: "string",
    },
}).pipe((o) => {
    return {
        ...o,
        data: {
            ...o.data,
            someExtraField: 5,
        },
    };
});

class EventListener<T extends typeof BaseEvent> {
    constructor(events: T[]) {
    }

    public on(event: T['infer']['type'], callback: (event: T['infer']) => void) {
    }
}

/* All the code below has type errors */
const listener = new EventListener([SomeEvent, SomePipedEvent]);

listener.on("some_event", (event) => {
    event.data.foo
});

listener.on("some_piped_event", (event) => {
    event.data.someExtraField
});
const BaseEvent = type({
    type: "string",
    timestamp: "number",
});

const SomeEvent = BaseEvent.and({
    type: "'some_event'",
    data: {
        foo: "string",
    },
});

const SomePipedEvent = BaseEvent.and({
    type: "'some_piped_event'",
    data: {
        bar: "string",
    },
}).pipe((o) => {
    return {
        ...o,
        data: {
            ...o.data,
            someExtraField: 5,
        },
    };
});

class EventListener<T extends typeof BaseEvent> {
    constructor(events: T[]) {
    }

    public on(event: T['infer']['type'], callback: (event: T['infer']) => void) {
    }
}

/* All the code below has type errors */
const listener = new EventListener([SomeEvent, SomePipedEvent]);

listener.on("some_event", (event) => {
    event.data.foo
});

listener.on("some_piped_event", (event) => {
    event.data.someExtraField
});
2 Replies
ssalbdivad
ssalbdivad•2w ago
There's not really a simple way to do this directly, no You could write a custom validator that would check the input of each Type to see if it matched, but not based on pure assignability the way you have it set up now
Bobakanoosh
BobakanooshOP•2w ago
Appreciate the response thanks!

Did you find this page helpful?